The present invention is related to the incorporation of annunciators into a liquid crystal display (LCD) assembly. Traditionally, such annunciators were housed in modules separate from the LCD assembly. However, the incorporation of annunciators into the LCD assembly has been pursued because of a demand for a more efficient use of available space as a result of product miniaturization, and because of the desire to centralize information devices.
There exist inherent problems with closely spaced and separately controlled annunciators which use color to convey additional information. The inherent problems include poor contrast when these annunciators are viewed in direct sunlight or bright ambient light. This is commonly termed "color washout." This problem is particularly acute when light emitting diodes are used to provide back lighting. Color washout may be partially addressed by using a reflector positioned on the rear of the LCD, colored to reflect the desired color for the annunciator, in conjunction with incandescent lamps for back lighting. Color contrast is improved but other problems persisted.
One such problem exist when the annunciators are viewed in low light. Light intended for a particular annunciator must be specifically targeted to that annundator display area to avoid inadvertent illumination of adjacent annunciators. This problem is commonly known as "color bleeding." Color bleeding also can occur from back lighting needed to view the main portion of the LCD. Additionally, it is desirable to use light emitting diode, rather than an incandescent lamp for back lighting, as the former is more reliable and has a longer life.
Thus, a LCD system which incorporates annunciators, and which provides sharp contrast in bright light, while producing similarly sharp images in low light, was long desired in the art. Furthermore, the use of light emitting diodes for back lighting was very desirable because of the relative low manufacturing cost, better reliability, and longer life, of light emitting diodes versus incandescent lamps.